The present invention relates generally to scuba diving, and more particularly, is directed to a device for providing safe ascent and decompression during dives. When returning to the surface from a deep water dive, it is necessary for the diver to decompress. To do so, the diver makes frequent stops on the way to the surface. Generally, the U.S. Navy Standard Air Decompression Table requires the diver to rise at a controlled rate of sixty feet per minute, while stopping at prescribed depths. This permits the nitrogen in the tissues of the diver to come out of solution and be expelled from the blood before expansion and before bubble formation constricts circulation. Otherwise, a situation known as the "bends" can occur, which can be deadly.
Because of the current in the water, if the diver merely ascends without any guide, the diver can find himself miles away from his boat. Accordingly, the diver will attempt to return to the surface along the anchor of the boat. However, frequently the anchor cannot be found, and the diver must return to the surface without the benefit of the anchor.
For this reason, a diver conventionally carries a decompression line in the form of a rope wrapped about a reel, the latter being held between the pair of oxygen tanks also supported on the diver's body. When the diver is ready to ascend, he ties an inflatable lift bag to the free end of the decompression line, and inflates the lift bag with oxygen from the tanks. The diver then holds onto the reel and permits the lift bag to rise to the surface, thereby paying out the rope from the reel. When the lift bag has reached the surface, the diver feels some slack in the line. Accordingly, the diver cuts the rope from the reel and ties the cut end of the rope to the ship wreck. Thereafter, the diver makes a planned ascent in order to properly decompress.
However, there are various problems that result from such an arrangement.
First, if many decompression lines are left in the water and tied to the ship wreck from many such decompression ascents, the water would be entangled with the lines, making it dangerous for future dives. Accordingly, the rope of the decompression line is made from hemp which decomposes over a period of time in the presence of salt water. In practice, a diver may carry the decompression line, while not using the same for many dives. For example, the diver may be able to use the anchor most of the time. However, after many dives, the diver may find himself in a predicament where he cannot find the anchor, and therefore, must use the decompression line. This, however, results in a problem. Specifically, since the decompression line has been subjected to salt water over many dives, it has at least partly decomposed and has therefore become weakened. As a result, the decompression line may break in use, which can be disastrous to the diver.
Second, because the decompression line is tied to the ship wreck, it cannot be retrieved. This adds to the cost of the dives, since the diver must periodically provide a new decompression line.
Third, before the diver releases the inflated lift bag, the diver must partially deflate his wet suit to eliminate some of his buoyancy, and thereby partially anchor himself to the ship wreck. Specifically, when the diver releases the inflated lift bag, the lift bag has a maximum rating for holding approximately 100 pounds of oxygen therein when inflated. However, if the diver were to inflate the lift bag to the full 100 pounds of pressure, even when partially anchoring himself, the large pressure in the lift bag would be too great for the diver, and the diver would be pulled upwardly. Accordingly, the lift bag is generally pressurized only to about 20 pounds. As a result, ascent of the lift bag is slower.
Fourth, and related to the third problem of inadequate inflation of the lift bag, the underinflated lift bag may not break through to the surface of the water, but rather, will generally remain a distance below the surface of the water. This is because the current will carry the underinflated bag after the opposite end of the decompression line is tied to the ship wreck, causing the lift bag to fall below the surface of the water. In such case, the lift bag will drift with the current somewhat and will therefore not provide a straight ascent for the diver. As a result, the diver, as he nears the position of the lift bag during ascent, must dart up the decompression line, further inflate the lift bag to full capacity and then dart back down the lift line to the previous decompression position. The diver will generally have about 60 seconds to perform this action before the adverse effects of a too quick decompression will affect him. This, of course, presents a dangerous situation to the diver.
Fifth, the decompression line and reel are relatively large and thereby carried on the back of the diver between the oxygen tanks. Because the decompression line is made from hemp, it must be relatively thick to provide sufficient strength, for example, on the order of one-quarter inch. This adds to the already approximately 200 pounds that the diver is carrying.
Sixth, the diver constantly bangs the tanks and the decompression line while swimming through the small openings in a ship wreck. As a result of these constant impacts and rubbing actions, the decompression line tends to become frayed, which can result in damage to the decompression line.